1. Field of the Invention
The present invention relates to an image forming apparatus which forms an image on an image-formation medium by jetting a liquid from a nozzle, and an information recording medium in which a program for controlling the image forming apparatus is recorded.
2. Description of Related Art
Generally, an image forming apparatus, for example, an ink jet printer is provided with an ink-jet head which jets ink from a nozzle onto a recording medium and an ink tank which supplies the ink to the ink-jet head, on a carriage which is supported movably relative to the recording medium. To the ink tank, ink is supplied, via a tube, from an ink cartridge disposed out of the carriage. In this ink jet printer, ink supplied from the ink cartridge via the tube is stored in the ink tank, and after air contained in the ink is separated, the ink stored in the ink tank is supplied to the ink-jet head.
For example, the ink jet printer described in US Patent Application Laid-open No. US2006/0001715 (Japanese Patent Application Laid-open No. 2004-255861) includes a suction cap which is brought into close contact with the nozzles of the ink-jet head and an air-discharge cap provided beside the suction cap, ink increased in viscosity is sucked by the suction cap from the nozzles, and air accumulated in the ink tanks is discharged by the air-discharge cap from air-discharge channels communicating with upper portions of the ink tanks.
Such an ink jet printer generally has a timer function, and performs above described ink suction and air discharge in predetermined periods. However, for example, if the power of an internal battery runs out in a state that the power supply is switched OFF or if the power supply is switched OFF in a state that the ink jet printer is provided with no internal battery, the ink jet printer becomes unable to measure the time. Therefore, thereafter, on the assumption that the ink jet printer was in an unusable state for a long period, that is, on the assumption that the ink in the nozzle is dried and a large amount of air in the ink grows as bubbles in the ink tank, a purge operation is performed for suctioning and discharging large amounts of ink and air.
However, in the ink jet printer described in US Patent Application Laid-open No. 2006/0001715, when the power source is switched ON after the ink jet printer becomes unable to measure the time, in addition to discharge of a large amount of inks from the nozzles as described above, along with air discharge from the upper portions of the ink tanks, inks are further sucked and discharged. If the air is sucked more than an air accumulation amount, the inks are also discharged from the air-discharge channels. Therefore, there has been a problem that the amount of inks to be consumed when the power supply is switched ON increases.